1. Field of the Invention
The present invention generally relates to defect management methods, reproduction methods, recording media, information recording apparatuses, and information reproduction apparatuses, and more particularly to a defect management method managing a defective area in an information recording medium, a reproduction method reproducing data from an information recording medium, a recording medium on which a program used in an information recording apparatus and an information reproduction apparatus is recorded, an information recording apparatus recording data on an information recording medium, and an information reproduction apparatus reproducing data from an information recording medium.
2. Description of the Related Art
Optical disks such as CDs (compact disks) and DVDs (digital versatile disks) have attracted attention as information recording media for recording data. As a result, optical disk units have been widely used as information recording apparatuses for recording data on optical disks and information reproduction apparatuses for reproducing data from optical disks.
Recordable CDs include CD-Rs and CD-RWs, and recordable DVDs include DVD-Rs, DVD+Rs, DVD-RWs, DVD+RWs, and DVD-RAMS. Data are recorded on and reproduced from these CDs and DVDs in compliance with their respective predetermined standards.
Conventionally, to those of a rewritable type of the above-described information recording media, defect management is applied as means for ensuring the reliability of recorded data. According to this defect management, a list relating a defective portion of an information recording medium with an area used instead of this defective portion is recorded in a predetermined replacement (spare) area of the recording medium. Control is performed so as to avoid use of the defective portion by referring to the list at the time of subsequent information recording and reproduction.
Next, a brief description is given of methods of replacing a defective area in defect management. Slipping and linear replacement are two types of methods that are generally employed to replace a defective area in defect management. Slipping detects a defective area, and uses the subsequent area instead of the defective area. Once “slipping (replacement)” occurs, each of a logical address accompanying data and a physical address indicating an area location slips by one. Linear replacement detects a defective area, and uses a replacement area pre-reserved in a location physically apart from the defective area. Linear replacement, in which the defective area and the replacement area to replace the defective area are physically apart from each other, may take more time to access the replacement area than slipping. In the DVD-RAM, for instance, slipping is applied to a primary defect, that is, a defect detected in disk initialization (formatting), and linear replacement is applied to a secondary defect, that is, a defect detected during recording of user data after the initialization. That is, both slipping and linear replacement are employed in the DVD-RAM. The defect information of the primary defect is recorded in a primary defect list (PDL), and the defect information of the secondary defect is recorded in a secondary defect list (SDL). In the DVD+RW, only linear replacement is applied.
The DVD+RW or DVD-RAM standards allow a user to request recording of data in the units of sectors. In the actual case of recording on an optical disk, however, the recording is performed using a recording block of a predetermined size called “ECC block” as a unit of recording. The ECC block is formed of a user data sector composed of 16 sectors. Accordingly, when the user requests data to be recorded in a sector, the data of an ECC block including the sector is temporarily read out from the optical disk, the read-out data is overwritten with the requested data, and the overwritten data is written back to the optical disk in the unit of the ECC block (recording block). This operation is referred to as RMW (read-modify-write).
When a secondary defect (a defect during recording of user data) is detected in the DVD-RAM or DVD+RW), the data is relocated to a replacement area in the units of ECC blocks. Accordingly, a replacement list for managing a defect is provided for each ECC block. That is, even if only a portion of the sectors of the ECC block is defective, the entire data of the ECC block is recorded in the replacement area. This is because if the ECC block includes a defective sector, it is highly probable that the data of the other sectors of the ECC block may not be read out either since data is subjected to error correction in the units of ECC blocks in the DVDS.
Therefore, if an error occurs in reading out the ECC block and the data of the ECC block cannot be read out during the above-described RMW operation, inconveniently, the ECC block cannot be replaced because all the data of the ECC block are not retained. Even if only the data that the user requests to be recorded in the sector is relocated to a replacement area, there is no choice but to record dummy data in the replacement area with respect to the other sectors. Therefore, if the user makes a request to reproduce data from a sector of the ECC block with respect to which the dummy data is recorded in the replacement area as a result of such data relocation, wrong data is returned to the user.
For instance, if the replacement list is to be prepared for each sector in order to cope with the above-described inconvenience, the number of replacement lists is 16 times that of the conventional method of performing defect management in the units of ECC blocks since each ECC block has 16 sectors. Accordingly, a large-capacity memory is required to retain such defect management information. Further, as described above, if an ECC block includes a defective sector, it is highly probable that the data of the other sectors of the ECC block may not be read out either. As a result, data is recorded in a replacement area in the units of ECC blocks. Accordingly, considering memory capacity, retaining a defect list for each sector has more demerits than merits.
Japanese Laid-Open Patent Application No. 2000-322835 discloses an apparatus for managing a defect of an information recording medium considering the presence or absence of data relocation (recording data in a replacement area instead of a defective area). This apparatus sets flag information indicating whether a defective area is replaced by a replacement area. When the apparatus determines by referring to the flag information that a defective area from which data is requested to be reproduced is not replaced by a replacement area, the apparatus reproduces the data from the defective area. However, when a user requests data to be recorded in a sector, and an ECC block including the sector cannot be read out, this apparatus cannot record the data in a replacement area, either.